Periodicity without rhythmicity

Abstract

Grid cells confer a spatial impression of an animal's environment on the brain. Their firing patterns in a cave-dwelling bat reopen old questions about how they do this, and pose some compelling new ones. See Letter p.103 Animals maintain a neural representation of space through the coordinated activity of grid, place and head-direction cells. Grid cells fire as the animal passes across the vertices of a periodic hexagonal grid depicting space. How these cells create the grid structure is still under debate, although recent work strongly proposes a model involving an oscillatory interference-driven transformation of temporal oscillations into the spatial grid. Yartsev et al. refute this model by characterizing a proper network of grid cells in an animal model, the Egyptian fruit bat, which naturally lacks oscillations required for the oscillatory interference model to produce grid structure. Besides directly characterizing grid cells in a non-rodent species, this study also argues against a major computational model of grid-cell production.